I've concluded that Orks have some of the best anti-flyer in 40k, besides their rate of fire.
Why? Wreckin' Balls, and more significantly, Grabbin' Klaws.
Grabbin' Klaws, on a 4+, prevent an enemy vehicle (or flyer, in this case) from moving - and seeing as flyers are vehicles that Crash and Burn if they don't move 18", this causes an instant kill!
The former Wreckin' Ball, mountable on Trukks, causes a S9 hit, also on a 4+, which is good for popping Drizzlepigeons and other light flyers, which is less impressive.
WAAAGH! ...and 40k banter thread because why not